Engine may implement a strategy called selective catalytic reduction (SCR) to reduce engine emission in exhaust systems. SCR is a process where a gaseous or liquid reductant (e.g., ammonia, urea, etc.,) is introduced into an exhaust conduit upstream of a catalyst. The SCR strategy converts NOx into N2 and water in the exhaust stream, reducing engine emissions and therefore the engine's impact on the environment. However, a number of factors can impact SCR performance. For example, decreased reductant injection atomization, caused by low pressure reductant injection, can negatively affect SCR operation. Reduced reductant evaporation, during cold starts for example, can also decrease NOx conversion in the catalyst. Incomplete flow mixing of the reductant and the exhaust gas can also decrease NOx conversion in the catalyst. In previous emission control systems a mixing device, downstream of a reductant injector, may be provided to improve SCR performance. However, the mixing device may be costly, bulky, and increase exhaust backpressure. Furthermore, mixing devices do not significantly improve reductant atomization and evaporation in the exhaust system. Thus, mixing devices may not enable the SCR catalyst to achieve desirable NOx conversion levels.
To address at least some of the aforementioned problems, an emission control system in an engine is provided. An emission control system for an engine is described herein. The emission control system includes a reductant injector extending into an exhaust conduit upstream of a catalyst. The reductant injector includes a reductant passage selectively receiving reductant from a reductant reservoir, an exhaust gas inlet receiving exhaust gas from the exhaust conduit, and an interior exhaust passage adjacent to the reductant passage, the interior exhaust passage receiving exhaust gas from the exhaust gas inlet and fluidly separated from the reductant passage.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.